The use of unsaturated polyester compounds in combination with thermoplastic resins and fillers to produce molding compositions is well known. These compositions, intended to polymerize when molded under heat and pressure, are generally combined with fillers and chopped glass, produced from roving, to produce molded products having appearance surfaces with a minimum of irregularities or undulations known as Class A surfaces.
The use of chopped glass as reinforcement in such molding compounds is well known. The chopped glass is produced in the form of individual strands which are sized, gathered into rovings, chopped to the desired length and incorporated into the resin composite prior to molding.
The sizes generally comprise a polyester emulsion base, a lubricant, film formers and the like and are extremely important in imparting to the reinforcing glass its ability to be wetted out by the molding compound. These sizes are also important in that they protect the glass in its handling subsequent to being sized and are influential in minimizing the amount of fuzz and fly which is produced on the glass, the fuzz and fly having a decided affect upon the appearance surface of the molded product.
The sized glass fibers generally are employed as reinforcement for sheet molding compounds (SMC) and bulk molding compounds (BMC).